Introduction

Kegalle Plantation PLC, a leading agricultural company in Sri Lanka, is renowned for its production of rubber, tea, and coconut across its extensive 10,000-hectare land base. Among its notable achievements, the Atala estate facility has excelled in producing high-quality crepe rubber, securing numerous national awards including the Best Crepe Rubber Factory Award. However, the crepe rubber manufacturing process generates substantial wastewater, necessitating effective treatment solutions to minimize environmental impact.

Wastewater Composition and Flow Estimation

The production of crepe rubber involves significant water usage for various processes such as washing, factory cleaning, and machinery cooling. This results in approximately 150 cubic meters of wastewater per day from the Atale estate facility. The effluent contains a mixture of organic and chemical pollutants, including proteins, sugars, organic acids, phosphorus, ammoniacal nitrogen, and organic nitrogen, which must be treated to prevent environmental contamination.

Existing Wastewater Treatment System

The current treatment system at Atale estate incorporates primary and secondary treatment processes. Wastewater initially passes through a rubber trap to remove debris, followed by anaerobic reactors and an aerated pond system. Despite these measures, the system has faced challenges in achieving optimal pollutant removal efficiencies, particularly for pH, Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Sulfide, and Total Suspended Solids (TSS).

Problems and Remedial Actions

The existing treatment system has encountered several issues:

• Rubber Trap: High hydraulic retention time at the old rubber trap has led to increased BOD levels in the effluent. To address this, it is recommended to recirculate effluent flow and introduce perforated baffle walls.
• Anaerobic Tanks: Odorous gases are released due to non-air-tight tanks. Implementing pressure relief valves and treating the gases before release is essential. Additionally, scum accumulation and coir degradation require the introduction of baffle walls and periodic media replacement.
• Aerobic Pond: Insufficient pond volume and water seepage issues necessitate modifications or replacement with a more effective treatment system.

Proposed Wastewater Treatment System

The proposed system includes significant upgrades to enhance treatment efficiency:

1. Anaerobic Baffled Reactor (ABR): This reactor uses baffles to compartmentalize the tank, allowing microbial granules to treat wastewater efficiently. The design aims for a 95% reduction in COD.
2. Activated Sludge System: An aerobic treatment process that uses microorganisms to decompose organic matter. This system includes an aeration tank, a final clarifier for solids separation, and return activated sludge equipment.
3. HDPE Flexible Cover System for Anaerobic Tank: For the first time in Sri Lanka, the use of High-Density Polyethylene (HDPE) flexible cover systems for anaerobic tanks was implemented in this project. These covers provide an effective solution for managing biogas emissions and odor control, while also enhancing the efficiency of the anaerobic digestion process. HDPE covers are highly durable and resistant to chemical and environmental degradation, making them ideal for long-term use in wastewater treatment facilities. By preventing the escape of harmful gases and reducing the infiltration of rainwater, HDPE covers help maintain optimal conditions within the tanks, ensuring more efficient breakdown of organic matter. Moreover, the captured biogas can be harnessed as a renewable energy source, contributing to the sustainability of the treatment process. The use of HDPE flexible covers represents a significant step forward in improving the operational and environmental performance of anaerobic digestion systems.

Conclusion

The proposed upgrades to the wastewater treatment system at Kegalle Plantation’s Atale estate aim to significantly improve the efficiency of pollutant removal, ensuring compliance with environmental standards. These sustainable management practices not only protect the environment but also reinforce the company’s commitment to responsible production processes. By implementing these advanced treatment solutions, Kegalle Plantation continues to lead in both agricultural excellence and environmental stewardship.